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From: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
To: linux-kernel@vger.kernel.org
Cc: Greg Kroah-Hartman <gregkh@linuxfoundation.org>,
	stable@vger.kernel.org,
	syzbot+a70e2ad0879f160b9217@syzkaller.appspotmail.com,
	Anand Jain <anand.jain@oracle.com>,
	Desmond Cheong Zhi Xi <desmondcheongzx@gmail.com>,
	David Sterba <dsterba@suse.com>
Subject: [PATCH 4.19 04/30] btrfs: fix rw device counting in __btrfs_free_extra_devids
Date: Mon,  2 Aug 2021 15:44:42 +0200	[thread overview]
Message-ID: <20210802134334.222025444@linuxfoundation.org> (raw)
In-Reply-To: <20210802134334.081433902@linuxfoundation.org>

From: Desmond Cheong Zhi Xi <desmondcheongzx@gmail.com>

commit b2a616676839e2a6b02c8e40be7f886f882ed194 upstream.

When removing a writeable device in __btrfs_free_extra_devids, the rw
device count should be decremented.

This error was caught by Syzbot which reported a warning in
close_fs_devices:

  WARNING: CPU: 1 PID: 9355 at fs/btrfs/volumes.c:1168 close_fs_devices+0x763/0x880 fs/btrfs/volumes.c:1168
  Modules linked in:
  CPU: 0 PID: 9355 Comm: syz-executor552 Not tainted 5.13.0-rc1-syzkaller #0
  Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 01/01/2011
  RIP: 0010:close_fs_devices+0x763/0x880 fs/btrfs/volumes.c:1168
  RSP: 0018:ffffc9000333f2f0 EFLAGS: 00010293
  RAX: ffffffff8365f5c3 RBX: 0000000000000001 RCX: ffff888029afd4c0
  RDX: 0000000000000000 RSI: 0000000000000001 RDI: 0000000000000000
  RBP: ffff88802846f508 R08: ffffffff8365f525 R09: ffffed100337d128
  R10: ffffed100337d128 R11: 0000000000000000 R12: dffffc0000000000
  R13: ffff888019be8868 R14: 1ffff1100337d10d R15: 1ffff1100337d10a
  FS:  00007f6f53828700(0000) GS:ffff8880b9a00000(0000) knlGS:0000000000000000
  CS:  0010 DS: 0000 ES: 0000 CR0: 0000000080050033
  CR2: 000000000047c410 CR3: 00000000302a6000 CR4: 00000000001506f0
  DR0: 0000000000000000 DR1: 0000000000000000 DR2: 0000000000000000
  DR3: 0000000000000000 DR6: 00000000fffe0ff0 DR7: 0000000000000400
  Call Trace:
   btrfs_close_devices+0xc9/0x450 fs/btrfs/volumes.c:1180
   open_ctree+0x8e1/0x3968 fs/btrfs/disk-io.c:3693
   btrfs_fill_super fs/btrfs/super.c:1382 [inline]
   btrfs_mount_root+0xac5/0xc60 fs/btrfs/super.c:1749
   legacy_get_tree+0xea/0x180 fs/fs_context.c:592
   vfs_get_tree+0x86/0x270 fs/super.c:1498
   fc_mount fs/namespace.c:993 [inline]
   vfs_kern_mount+0xc9/0x160 fs/namespace.c:1023
   btrfs_mount+0x3d3/0xb50 fs/btrfs/super.c:1809
   legacy_get_tree+0xea/0x180 fs/fs_context.c:592
   vfs_get_tree+0x86/0x270 fs/super.c:1498
   do_new_mount fs/namespace.c:2905 [inline]
   path_mount+0x196f/0x2be0 fs/namespace.c:3235
   do_mount fs/namespace.c:3248 [inline]
   __do_sys_mount fs/namespace.c:3456 [inline]
   __se_sys_mount+0x2f9/0x3b0 fs/namespace.c:3433
   do_syscall_64+0x3f/0xb0 arch/x86/entry/common.c:47
   entry_SYSCALL_64_after_hwframe+0x44/0xae

Because fs_devices->rw_devices was not 0 after
closing all devices. Here is the call trace that was observed:

  btrfs_mount_root():
    btrfs_scan_one_device():
      device_list_add();   <---------------- device added
    btrfs_open_devices():
      open_fs_devices():
        btrfs_open_one_device();   <-------- writable device opened,
	                                     rw device count ++
    btrfs_fill_super():
      open_ctree():
        btrfs_free_extra_devids():
	  __btrfs_free_extra_devids();  <--- writable device removed,
	                              rw device count not decremented
	  fail_tree_roots:
	    btrfs_close_devices():
	      close_fs_devices();   <------- rw device count off by 1

As a note, prior to commit cf89af146b7e ("btrfs: dev-replace: fail
mount if we don't have replace item with target device"), rw_devices
was decremented on removing a writable device in
__btrfs_free_extra_devids only if the BTRFS_DEV_STATE_REPLACE_TGT bit
was not set for the device. However, this check does not need to be
reinstated as it is now redundant and incorrect.

In __btrfs_free_extra_devids, we skip removing the device if it is the
target for replacement. This is done by checking whether device->devid
== BTRFS_DEV_REPLACE_DEVID. Since BTRFS_DEV_STATE_REPLACE_TGT is set
only on the device with devid BTRFS_DEV_REPLACE_DEVID, no devices
should have the BTRFS_DEV_STATE_REPLACE_TGT bit set after the check,
and so it's redundant to test for that bit.

Additionally, following commit 82372bc816d7 ("Btrfs: make
the logic of source device removing more clear"), rw_devices is
incremented whenever a writeable device is added to the alloc
list (including the target device in btrfs_dev_replace_finishing), so
all removals of writable devices from the alloc list should also be
accompanied by a decrement to rw_devices.

Reported-by: syzbot+a70e2ad0879f160b9217@syzkaller.appspotmail.com
Fixes: cf89af146b7e ("btrfs: dev-replace: fail mount if we don't have replace item with target device")
CC: stable@vger.kernel.org # 5.10+
Tested-by: syzbot+a70e2ad0879f160b9217@syzkaller.appspotmail.com
Reviewed-by: Anand Jain <anand.jain@oracle.com>
Signed-off-by: Desmond Cheong Zhi Xi <desmondcheongzx@gmail.com>
Signed-off-by: David Sterba <dsterba@suse.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
---
 fs/btrfs/volumes.c |    1 +
 1 file changed, 1 insertion(+)

--- a/fs/btrfs/volumes.c
+++ b/fs/btrfs/volumes.c
@@ -995,6 +995,7 @@ again:
 		if (test_bit(BTRFS_DEV_STATE_WRITEABLE, &device->dev_state)) {
 			list_del_init(&device->dev_alloc_list);
 			clear_bit(BTRFS_DEV_STATE_WRITEABLE, &device->dev_state);
+			fs_devices->rw_devices--;
 		}
 		list_del_init(&device->dev_list);
 		fs_devices->num_devices--;



  parent reply	other threads:[~2021-08-02 13:55 UTC|newest]

Thread overview: 36+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2021-08-02 13:44 [PATCH 4.19 00/30] 4.19.201-rc1 review Greg Kroah-Hartman
2021-08-02 13:44 ` [PATCH 4.19 01/30] virtio_net: Do not pull payload in skb->head Greg Kroah-Hartman
2021-08-02 13:44 ` [PATCH 4.19 02/30] gro: ensure frag0 meets IP header alignment Greg Kroah-Hartman
2021-08-02 13:44 ` [PATCH 4.19 03/30] x86/asm: Ensure asm/proto.h can be included stand-alone Greg Kroah-Hartman
2021-08-02 13:44 ` Greg Kroah-Hartman [this message]
2021-08-02 13:44 ` [PATCH 4.19 05/30] x86/kvm: fix vcpu-id indexed array sizes Greg Kroah-Hartman
2021-08-02 13:44 ` [PATCH 4.19 06/30] ocfs2: fix zero out valid data Greg Kroah-Hartman
2021-08-02 13:44 ` [PATCH 4.19 07/30] ocfs2: issue zeroout to EOF blocks Greg Kroah-Hartman
2021-08-02 13:44 ` [PATCH 4.19 08/30] can: raw: raw_setsockopt(): fix raw_rcv panic for sock UAF Greg Kroah-Hartman
2021-08-02 13:44 ` [PATCH 4.19 09/30] can: mcba_usb_start(): add missing urb->transfer_dma initialization Greg Kroah-Hartman
2021-08-02 13:44 ` [PATCH 4.19 10/30] can: usb_8dev: fix memory leak Greg Kroah-Hartman
2021-08-02 13:44 ` [PATCH 4.19 11/30] can: ems_usb: " Greg Kroah-Hartman
2021-08-02 13:44 ` [PATCH 4.19 12/30] can: esd_usb2: " Greg Kroah-Hartman
2021-08-02 13:44 ` [PATCH 4.19 13/30] NIU: fix incorrect error return, missed in previous revert Greg Kroah-Hartman
2021-08-02 13:44 ` [PATCH 4.19 14/30] nfc: nfcsim: fix use after free during module unload Greg Kroah-Hartman
2021-08-02 13:44 ` [PATCH 4.19 15/30] cfg80211: Fix possible memory leak in function cfg80211_bss_update Greg Kroah-Hartman
2021-08-02 13:44 ` [PATCH 4.19 16/30] netfilter: conntrack: adjust stop timestamp to real expiry value Greg Kroah-Hartman
2021-08-02 13:44 ` [PATCH 4.19 17/30] netfilter: nft_nat: allow to specify layer 4 protocol NAT only Greg Kroah-Hartman
2021-08-02 13:44 ` [PATCH 4.19 18/30] i40e: Fix logic of disabling queues Greg Kroah-Hartman
2021-08-02 13:44 ` [PATCH 4.19 19/30] i40e: Fix log TC creation failure when max num of queues is exceeded Greg Kroah-Hartman
2021-08-02 13:44 ` [PATCH 4.19 20/30] tipc: fix sleeping in tipc accept routine Greg Kroah-Hartman
2021-08-02 13:44 ` [PATCH 4.19 21/30] mlx4: Fix missing error code in mlx4_load_one() Greg Kroah-Hartman
2021-08-02 13:45 ` [PATCH 4.19 22/30] net: llc: fix skb_over_panic Greg Kroah-Hartman
2021-08-02 13:45 ` [PATCH 4.19 23/30] net/mlx5: Fix flow table chaining Greg Kroah-Hartman
2021-08-02 13:45 ` [PATCH 4.19 24/30] sctp: fix return value check in __sctp_rcv_asconf_lookup Greg Kroah-Hartman
2021-08-02 13:45 ` [PATCH 4.19 25/30] tulip: windbond-840: Fix missing pci_disable_device() in probe and remove Greg Kroah-Hartman
2021-08-02 13:45 ` [PATCH 4.19 26/30] sis900: " Greg Kroah-Hartman
2021-08-02 13:45 ` [PATCH 4.19 27/30] can: hi311x: fix a signedness bug in hi3110_cmd() Greg Kroah-Hartman
2021-08-02 13:45 ` [PATCH 4.19 28/30] powerpc/pseries: Fix regression while building external modules Greg Kroah-Hartman
2021-08-02 13:45 ` [PATCH 4.19 29/30] Revert "perf map: Fix dso->nsinfo refcounting" Greg Kroah-Hartman
2021-08-02 13:45 ` [PATCH 4.19 30/30] i40e: Add additional info to PHY type error Greg Kroah-Hartman
2021-08-02 17:50 ` [PATCH 4.19 00/30] 4.19.201-rc1 review Pavel Machek
2021-08-03 10:10 ` Naresh Kamboju
2021-08-03 10:37 ` Sudip Mukherjee
2021-08-03 19:15 ` Guenter Roeck
2021-08-05  1:08 ` Samuel Zou

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